1. Field of the Invention
The present invention relates to a fixing belt, a fixing device, and an image forming apparatus.
2. Description of Related Art
A fixing device employed in an image forming apparatus, such as a copier or a laser beam printer, generally brings a heated fixing belt into contact with recording media that bear unfixed toner images, thereby fixing toner images on the recording media. Then, the recording media bearing the fixed toner images are separated from the fixing belt. Such a fixing belt is, for example, an endless belt including a base layer, an elastic layer, and a release layer laminated in this order.
As such a fixing belt, a fixing belt including two or more elastic layers each having a different thermal conductivity is known from the viewpoint of image smoothness and energy saving (e.g., Japanese Patent Application Laid-Open No. 2005-084134 (hereinafter, “Patent Literature (PTL)” 1)). Also, as such a fixing belt, a fixing belt including two or more elastic layers each having a different heat-resistant temperature is known from the viewpoint of durability (e.g., Japanese Patent Application Laid-Open No. 2005-055470 (hereinafter, “PTL” 2).
A hardness of a fixing belt affects fixability of toner images and separability of recording media. More specifically, adhesion between a fixing belt and a recording medium generally lowers as the hardness of the fixing belt increases. As a result, fixability of toner images tends to lower as separability of recording media improves. The fixing belts described in PTLs 1 and 2 occasionally fail to achieve expected fixability and separability. Accordingly, an electrophotographic image forming apparatus including each of the fixing belts described in PTLs 1 and 2 occasionally fails to form images in a stable manner due to jams of recording media. In the specification, the term “toner image” refers to an aggregated state of a toner as an image.